Particulate matter contamination

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Temperature. The temperature for combustion processes must be balanced between the minimum temperature required to combust the original contaminants and any intermediate by-products completely and the maximum temperature at which the ash becomes molten. Typical operating temperatures for thermal processes are incineration (750—1650°C), catalytic incineration (315—550°C), pyrolysis (475—815°C), and wet air oxidation (150—260°C at 10,350 kPa) (15). Pyrolysis is thermal decomposition in the absence of oxygen or with less than the stoichiometric amount of oxygen required. Because exhaust gases from pyrolytic operations are somewhat "dirty" with particulate matter and organics, pyrolysis is not often used for hazardous wastes. 

Foulants enter a cooling system with makeup water, airborne contamination, process leaks, and corrosion. Most potential foulants enter with makeup water as particulate matter, such as clay, sdt, and iron oxides. Insoluble aluminum and iron hydroxides enter a system from makeup water pretreatment operations. Some well waters contain high levels of soluble ferrous iron that is later oxidized to ferric iron by dissolved oxygen in the recirculating cooling water. Because it is insoluble, the ferric iron precipitates. The steel corrosion process is also a source of ferrous iron and, consequendy, contributes to fouling. 

Figure 30-lE includes a hot ESP for fly ash collection prior to a catalytic NO , unit. Having a hot ESP dictates the use of a conventional wet scrubber and perhaps the need for a second particulate matter control device at the end of the system. Fly ash and scrubber sludge would be separate byproducts, but sludge could be contaminated with NH4 from the catalytic NO process. 

To remove insoluble contaminants, various types of full-flow filters can be used. Two general types are usually selected surface filters and depth filters. Both types of filters are effective for the removal of particulate matter. 

If the waste stream has a high content of fine particulate matter then, by isolating piarticulate matter, most of the contamination would be isolated. 

In recapping, DAF is the process of removing suspended solids, oils and other contaminants via the use of bubble flotation. Air is dissolved into the water, then mixed with the wastestream and released from solution while in intimate contact with the contaminants. Air bubbles form, saturated with air, mix with the wastewater influent and are injected into the DAF separation chamber. The dissolved air then comes out of solution, producing literally millions of microscopic bubbles. These bubbles attach themselves to the particulate matter and float then to the surface where they are mechanically skimmed and removed from the tank. Most systems are versatile enough to remove not only finely divided suspended solids, but fats, oils and grease (FOG). Typical wastes handled include various suspended... 

Filter life Measure of the duration of a filter s useful service. This is based on the amount of standard contaminant required to cause differential pressure to increase to an unacceptable level-typically 2-4 times the initial differential pressure, a 50-80% drop in initial flow, or a downstream measure of unacceptable particulate. Filter media A porous material for separating suspended particulate matter from fluid. 

The bench should be supplied with HEPA-filtered unidirectional airflow, having a velocity sufficient to sweep particulate matter away from the working area. Normally a velocity of 0.45 m s plus or minus 20% is adequate. It is important to monitor the air velocity at suitable intervals because significant reduction in velocity or uniformity in velocity can increase the risk of contamination. 

Ejector A device used to provide a primary airstream into which the contaminated air is entrained for subsequent removal. Used when corrosive products, high temperatures, fan blockage by particulate matter, or fire or explosion risk make a fan unsuitable. 

Maintaining hydraulic fluid within allowable contamination limits for both water and particulate matter is cmcial to the care and protection of hydraulic equipment. Filters will provide adequate control of the particular contamination problem during all normal hydraulic system operations if the filtration system is installed properly and filter maintenance is performed properly. Filter maintenance includes changing elements at proper intervals. 

In Mexico City, several air quality parameters are measured continuously by an Automated Monitoring Network operated by the Under Secretariat of Ecology. Carbon monoxide, particulate matter, sulfur dioxide, nitrogen oxide, and ozone are the contaminants exceeding Air Quality Standards. Emissions produced by 2.7 million vehicles and 35,000 commercial and industrial outfits are not easily dispersed in a Valley located at 2240 m and surrounded by two mountain chains which hinder air circulation. An Integral Program, recently established to alleviate pollution, is briefly described. 

Filtered air may be used to purge a complete room, or it m be confined to a specific area and incorporate the principle of laminar flow, which permits operations to be carried out in a gentle current of sterile air. The direction of the airflow may be horizontal or vertical, depending upon the type of equipment being nsed, the type of operation and the material being handled. It is important that there is no obstruction between the air supply and the exposed product, since this may resnlt in the deflection of microorganisms or particulate matter fiom a non-sterile surface and canse contamination. Airflow gauges are essential to monitor that the correct flow rate is obtained in laminar flow units and in complete suites to ensure that a positive pressure fiom clean to less clean areas is always maintained. 

Particulate, as well as microbial, contamination must be guarded against when sterile products are being manufactured. Thus, walls, ceilings and floors should possess smooth, impervious surfaces which will (i) prevent the accumulation of dust or other particulate matter and (ii) allow for easy and repeated cleaning and disinfection. For the same reasons, where walls and floors or ceilings meet, covings should be used. 

The products of incomplete combustion may be associated with particulate matter before their discharge into the atmosphere, and these may ultimately enter the aquatic and terrestrial environments in the form of precipitation and dry deposition. It is therefore essential to ensure total destruction of the contaminants, generally by raising the temperature. The spectrum of compounds that have been examined is quite extensive, and several of them are produced by reactions between hydrocarbons and inorganic sulfur or nitrogen constituents of air. Some illustrative examples involving other types of reaction include the following ... 

Plourde Y, Lucotte M, Pichet P. 1997. Contribution of suspended particulate matter and zooplankton to methyhnercury contamination of the food chain in mid-northern Quebec (Canada) reservoirs. Can J Fish Aquat Sci 54 821-831. 

Primary copper processing results in air emissions, process wastes, and other solid-phase wastes. Particulate matter and sulfur dioxide are the principal air contaminants emitted by primary copper smelters. Copper and iron oxides are the primary constituents of the particulate matter, but other oxides, such as arsenic, antimony, cadmium, lead, mercury, and zinc, may also be present, with metallic sulfates and sulfuric acid mist. Single-stage electrostatic precipitators are widely used in the primary copper industry to control these particulate emissions. Sulfur oxides contained in the off-gases are collected, filtered, and made into sulfuric acid. 

Long-lasting measurements of the environmental background contamination (particulate matter and air in areas far away from cities and industry) and analytical data of food and biota prove that the transport into the environment is slowly decreasing. The actual emissions in Europe decreased from 500 Mg/year (1990)... 

Acrylonitrile is both readily volatile in air (0.13 atm at 23° C) (Mabey et al. 1982) and highly soluble in water (79,000 mg/L) (Klein et al. 1957). These characteristics dominate the behavior of acrylonitrile in the environment. While present in air, acrylonitrile has little tendency to adsorb to particulate matter (Cupitt 1980), so air transport of volatilized material is determined mainly by wind speed and direction. Similarly, acrylonitrile dissolved in water has only a low tendency to adsorb to suspended soils or sediments (Roy and Griffin 1985), so surface transport is determined by water flow parameters. Based on its relatively high water solubility, acrylonitrile is expected to be higly mobile in moist soils. In addition, acrylonitrile may penetrate into groundwater from surface spills or from contaminated surface water. The high vapor pressure indicates that evaporation from dry soil samples is expected to occur rapidly (EPA 1987). 

---